The volumetric erosion of electrical contacts

In this paper a method for measuring the volume of eroded electrical contacts is presented. The main emphasis is on the measurement of volume relative to a contact support surface, allowing severely eroded contacts to be measured. A noncontact system is described, which allows contacts to be evaluated for volume change without the contact being removed from contact supports. The accuracy of the measurement method is discussed and results show how the volume measurement can be used to evaluate contact performance. Results are presented on the erosion characteristics of Ag/SnO/sub 2/ contacts used in automotive relays. A new measurement methodology is presented which will allow for the evaluation of the performance of relay contacts in devices.